Answers

You have to do all of the challenge matches in Rey Mysterio's RTWM and then talk to him in the Green Room at WrestleMania. There will be one more challenge match slot by the time you are at WrestleMania. Sadly, I don't know where the challenge matches are in Rey's RTWM. You can also unlock Stone Cold Steve Austin by doing Christian's RTWM and completing all of the challenge matches. You can also unlock The Rock the same way in the VS. Undertaker RTWM.